I don’t know who thought of this, but if you turn off all sounds in Windows, you’ll start getting beeps through the PC speaker.
Microsoft did not give us an easy way to disable them (like an option on the sounds dialog, maybe? 🙂 ) so you’ll have to do it via the Command Prompt (as the Administrator):
Temporary stop: net stop beep
Permanent stop: sc config beep start= disabled
Make sure you have the space between the equals sign and the disabled text.